QAYYARA, Iraq Nearly 1,000 people have been treated for breathing problems linked to fumes from a burning sulphur plant set ablaze during fighting with Islamic State near Mosul and U.S. officials say U.S. forces at a nearby airfield are wearing protective masks.The Qayyara West airfield is the main U.S. hub to support Iraqi-led operations to retake the city of Mosul from Islamic State. There are about 5,000 U.S. troops in Iraq but the U.S. military has not disclosed the number of personnel at the airfield."The winds have actually shifted south, so, as a precautionary measure, the troops at Qayyara West have donned their personal protective equipment – continuing their operations at this point in time," an official said on Saturday, speaking on condition of anonymity.It was not immediately clear if the troops had been ordered to wear the protective gear or if they had elected to, a second official said.A Reuters reporter in Qayyara saw Iraqi soldiers wearing gas masks on top of their heads, ready to pull them down

Nearly 1,000 people have been treated for breathing problems linked to the toxic gases, sources at the hospital in Qayyara said, reporting no death at the medical facility itself.A cloud of white smoke blanketed the region to the north, where the factory is located, mingling with black fumes from oil wells that the militants torched to cover their moves.

Air samples from Qayyara West were sent to the U.S. Defense Threat Reduction Agency for analysis as to "what, if any concerns, may result," another U.S. official said. The U.S officials said Islamic State set the sulfur plant ablaze on Thursday during fighting around al-Mishraq, which is south of Mosul. Iraqi state TV said it the fire has been put out Saturday.Operation Inherent Resolve, the official name of the U.S-led anti-Islamic State coalition, said it in a statement on Saturday it had provided more than 24,000 protective chemical masks to the Iraqi security forces and the allied Kurdish Peshmerga fighters during the training for the Mosul offensive.

Separately, the coalition said it the airfield of Qayyara started receiving on Friday fixed wing cargo aircraft, a U.S. Air Force engineers with the 1st Expeditionary Civil Engineer Group repaired it. (Writing by Maher Chmaytelli; Editing by Jeremy Gaunt)

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